#1
11-19-2013, 02:18 PM
 Victorsaur LawnSite Member Join Date: Feb 2011 Location: Asheville, NC Posts: 81
Lime application formula

What caught my eye was the lime application formula which is:

tons CaCO3 / acre = Ac [(desired pH - soil pH) / (6.6 - soil pH)]

What that means is if the soil is 6.6 you apply infinite lime. If the soil pH is 6.5 you apply twice as much as if it was 6.4... This formula screams inaccuracy and I was curious if anybody could help with some direction given soil acidity, pH, etc.
#2
11-19-2013, 05:49 PM
 heritage LawnSite Bronze Member Join Date: Aug 2003 Location: New Jersey Posts: 1,224
Quote:
 Originally Posted by Victorsaur I was provided with a link to this article by heritage: What caught my eye was the lime application formula which is: tons CaCO3 / acre = Ac [(desired pH - soil pH) / (6.6 - soil pH)] What that means is if the soil is 6.6 you apply infinite lime. If the soil pH is 6.5 you apply twice as much as if it was 6.4... This formula screams inaccuracy and I was curious if anybody could help with some direction given soil acidity, pH, etc.
If your mineral soil was 6.6 you would not add any lime.
#3
11-19-2013, 10:32 PM
 Victorsaur LawnSite Member Join Date: Feb 2011 Location: Asheville, NC Posts: 81
Quote:
 Originally Posted by heritage If your mineral soil was 6.6 you would not add any lime.
In other words the formula can be simplified to:

tons CaCO3 / acre = Ac

Lol.
#4
11-20-2013, 10:22 AM
 Kiril LawnSite Fanatic Join Date: Jun 2007 Location: District 9 CA Posts: 18,343
Quote:
 Originally Posted by Victorsaur In other words the formula can be simplified to: tons CaCO3 / acre = Ac Lol.
You have misunderstood and misrepresented the formula, which is the reason for your confusion.
#5
11-20-2013, 01:17 PM
 Victorsaur LawnSite Member Join Date: Feb 2011 Location: Asheville, NC Posts: 81
Quote:
 Originally Posted by Kiril You have misunderstood and misrepresented the formula, which is the reason for your confusion.
According to the formula the bracket portion will not differ greatly from the number 1 because 6.6 happens to be an ideal soil pH. If 6.6 is taken as an ideal pH level then the bracket portion is equal to 1. My confusion lies in the simplicity of the formula and questions its' accuracy. I was merely pointing out that if the target pH varies greatly from 6.6 then the formula makes little logical sense as a way of providing one reason why I distrust this formula. I am asking if this is the standard formula or what others use, although I understand that formulas vary greatly from place to place.
#6
11-21-2013, 10:53 AM
 Kiril LawnSite Fanatic Join Date: Jun 2007 Location: District 9 CA Posts: 18,343

The procedure for measuring exchangeable Al+3 is not well suited for routine soil testing procedure. For this reason a buffer solution pH 6.6 is used to measure extractable acidity (Ac) in North Carolina soils. The buffered solution extracts both exchangeable Al3+ and the pH dependent acidity (H+) which becomes ionized up to pH 6.6. The lime rate to apply is calculated with the following equation.

tons CaCO3 / acre = Ac [(desired pH - soil pH) / (6.6 - soil pH)]

The desired pH for a soil is the pH at which the activity of Al+3 is neutralized. The effect of soil organic matter in decreasing the activity of Al+3 has been taken into account by establishing desired pH for each of three classes of soils (mineral, mineral-organic and organic) based on their organic matter content. The desired pH at which exchangeable Al+3 is essentially neutralized is 6 for mineral soils, 5.5 for mineral-organic soils, and 5 for organic soils.
Furthermore, without a value for Ac the formula is worthless.
#7
11-21-2013, 05:34 PM
 Victorsaur LawnSite Member Join Date: Feb 2011 Location: Asheville, NC Posts: 81
Quote:
 Originally Posted by Kiril From your link. http://www.soil.ncsu.edu/about/century/soilacidity.html The procedure for measuring exchangeable Al+3 is not well suited for routine soil testing procedure. For this reason a buffer solution pH 6.6 is used to measure extractable acidity (Ac) in North Carolina soils. The buffered solution extracts both exchangeable Al3+ and the pH dependent acidity (H+) which becomes ionized up to pH 6.6. The lime rate to apply is calculated with the following equation. tons CaCO3 / acre = Ac [(desired pH - soil pH) / (6.6 - soil pH)] The desired pH for a soil is the pH at which the activity of Al+3 is neutralized. The effect of soil organic matter in decreasing the activity of Al+3 has been taken into account by establishing desired pH for each of three classes of soils (mineral, mineral-organic and organic) based on their organic matter content. The desired pH at which exchangeable Al+3 is essentially neutralized is 6 for mineral soils, 5.5 for mineral-organic soils, and 5 for organic soils.Furthermore, without a value for Ac the formula is worthless.
Ok, thanks Kiril. For all values of desired pH less than 6.6 this formula makes sense.

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